Occasionally it is desired to convert binary numbers to decimal (usually for a decimal readout), or rarely, a decimal number to binary.
Typically the first step for displaying binary number in a decimal display is to convert the binary number to BCD (Binary Coded Decimal).
(BCD is the representation of each of the decimal digits one through 9 by the equivalent 4-bit binary number.)
This BCD number can then be easily decoded into the individual decimal display digits.
[/quote]
Read more here.